In 1990, Kodak introduced

Cinema Digital Sound (CDS)

with the premiere of

Dick Tracy. The CDS system was a technology which used Delta Moduation
compression with a data reduction of 4:1. CDS was a 5.1 system with a left, center, right, left
surround, right surround, and low frequency effects channel and was available in both 35mm and
70mm formats. CDS was an optical technology with an array of pixels in place of the analogue
soundtrack. Unlike its successors, CDS had no analog backup. It failed in several screenings and
that seemed to mark its doom.

In 1992,

Dolby Laboratories

released

Dolby Digital

with the movie

Batman Returns. Dolby Digital is a 5.1 format based on Dolby's

AC-3

data reduction algorithm. The digital data is placed between the sprocket
holes, which allows the retention of the analogue tracks. This allows

only one release print to be made for each theater as well as an analogue backup. Dolby Digital has
been know under several names including Dolber Stereo SR*D in the theaters and Dolby Surround
Digital AC-3 for the home. Dolby Digital has been chosen as the sound standard for

DVD

released

in the United States as well as the new

DTV

standard for US television.

In 1993, two new digital sound formats were released: DTS and SDDS.

Digital

Theater Systems (DTS)

premiered with the film Jurassic Park. It involves

synchronizing a CD-ROM with the film by using a timecode track between the
picture and analogue soundtrack. It uses a data reduction algorithm they call
"Coherent Acoustics" to reduce the data required for this 5.1 system. Coherent Acoustics seems to
be a variation of Adaptive Delta Pulse Code Modulation (ADPCM). DTS is the first system since
CDS that is available for both 35mm and 70mm. Like Dolby Digital, DTS uses the analoug
soundtrack as a backup.

Sony Dynamic Digital Sound (SDDS)

premiered with the film Last Action Hero.

SDDS is unique in that it supports 7.1 sound. In has left, mid-left, center, mid-right,
right, left surround, right surround, and low frequency effects channel. It's is the first
system to exceed Cinerama as far as number of channels are concerned. The SDDS

digital data is on both edges of the 35mm piece of the film. This is redundant information to provide
added error correction. If that fails, the analog soundtrack provides additional support. SDDS uses
the

ATRAC

data reduction system originally developed for the Minidisc.